Journal of Vestibular Research - Volume 3, issue 3

Authors: Young, Laurence R.

Article Type: Editorial

DOI: 10.3233/VES-1993-3301

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 203-206, 1993

Authors: Clarke, Andrew H. | Teiwes, Winfried | Scherer, Hans

Article Type: Research Article

Abstract: The experimental concept and findings from a recent manned orbital spaceflight are described. Together with ongoing terrestrial and parabolic studies, the present experiment is intended to further our knowledge of the sensory integrative processing of information from the semicircular canals and the otolithic receptors, and to quantify the presumed otolithic adaptation to altered gravito-inertial force environments in a more reliable manner than to date. The experiment included measurement of the basic vestibulo-oculomotor response during active head rotation about each of the three orthogonal axes. Priority was given to the recording of ocular torsion, as elicited by head oscillation about the …roll axis, and thus due to the concomitant stimulation of the semicircular canals and otolith receptors. Videooculography was employed for the measurement of eye movements; head movement was measured by three orthogonally arranged angular rate sensors and a triaxial linear accelerometer device. All signals were recorded synchronously on a video/data recorder. Preliminary results indicate alterations in the torsional VOR under zero-g conditions, suggesting an adaptive modification of the torsional VOR gain over the course of the 6-day orbital flight. In addition, the inflight test findings yielded discrepancies between intended and performed head movement indicating impairment in sensorimotor coordination under prolonged microgravity conditions. Show more

Keywords: vestibulo-ocular reflex, ocular torsion, weightlessness, video-oculography

DOI: 10.3233/VES-1993-3302

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 207-218, 1993

Authors: Kornilova, L.N. | Grigorova, V. | Bodo, G.

Article Type: Research Article

Abstract: The vestibular system and vestibulo-visual interaction were examined in 11 astronauts by the electrooculographic (EOG) method during short- and long-term flights on days 2, 3, 5, 9, 22, 50, 164, and 169 (experiments OPTOKINES and LABYRINTH). In space (flight days 2 and 3), they showed enhanced spontaneous vertical nystagmus, and disorders of tracking of vertical and diagonal movements of the stimulus which improved after active head movements. Early increasing of the reactivity of the cupulo-endolymphatic system (flight days 2–3) was replaced after 5 days of flight with a reduction of the vestibular function and an increase of the significance of …the visual input in the formation of oculomotor responses to combined vestibulo-optokinetic stimulation. The type of spontaneous ocular reaction and vestibular stimulation of oculomotor activity under the conditions of weightlessness represented, on one band, the general responses of sensory systems to weightlessness and, on the other hand, specificity of integrating and adaptive processes. Show more

Keywords: vestibular function, vestibulo-oculomotor interaction, eye movements, weightiessness, cosmonauts

DOI: 10.3233/VES-1993-3303

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 219-230, 1993

Authors: Young, Laurence R. | Oman, Charles M. | Merfeld, Daniel | Watt, Douglas | Roy, Serge | DeLuca, Carlo | Balkwill, David | Christie, Jock | Groleau, Nicolas | Jackson, D. Keoki | Law, Glenn | Modestino, Sherry | Mayer, William

Article Type: Research Article

Abstract: The 4 payload crew members of the Spacelab Life Sciences 9-day space flight in 1991 were subjected to limited vestibular testing in flight as well as pre and post flight. Major differences in individual “perceptual style” appeared in their reaction to the visual-vestibular stimuli in the rotating dome experiment, and especially in the extent to which nondirectional tactile cues served to anchor the subjective vertical and body postural reactions. The ability of subjects to point to remembered target positions was degraded in space, which produced a tendency to point low in some subjects in flight. The eye movements and subjective …response to sudden stops and head pitching following continuous spinning (dumping) were measured both in space and on the ground. Although subjective duration of inflight rotation for the dumping tests was shorter than that for the preflight tests, the postrotatory nystagmus, with or without head pitch, was lengthened in time constant relative to preflight. Ground tests, in addition to the flight experiments, investigated the changes following in subjective and oculomotor reactions to whole body tilt, the ability to balance with eyes open and closed; leg muscle strength and stamina as related to posture; visual field dependence; and the perceptual and oculomotor reactions to horizontal linear acceleration. Several of these tests, as well as postflight measures of motion sickness susceptibility, revealed subtle evidence of neurovestibular alterations that lasted a week or more following the 10-day orbital exposure. Show more

Keywords: vestibular, posture, perception, adaptation, human, weightlessness

DOI: 10.3233/VES-1993-3304

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 231-239, 1993

Authors: Ross, Muriel D.

Article Type: Research Article

Abstract: Mammalian gravity receptors (maculas) are morphologically organized for weighted, parallel distributed processing of information. There are two basic circuits: 1) highly channeled, type I cell to calyx; and 2) distributed modifying, type II cells to calyces and processes. The latter circuit should be the more adaptable since it modifies final output. To test this hypothesis, rats were flown in microgravity for 9 days aboard a space shuttle and euthanized shortly after landing. Hair cells and ribbon synapses from maculas of 3 flight and 3 ground control rats were studied ultrastructurally in blocks of 50 serial sections. Synapses increased by approximately …41% in type I cells and by approximately 55% in type II cells in flight animals. There was a shift toward the spherular form of ribbon synapse in both types of hair cells in flight animals (P ⩽ 0.0001), a near doubling of pairs in the flight rats (P ⩽ 0.0001), and an increase, by a factor of 12, in groups of synapses in type II cells (P ⩽ 0.0001). Current findings tend to support the stated hypothesis and indicate that mature utricular hair cells retain synaptic plasticity, permitting adaptation to an altered gravitational environment. Show more

Keywords: utricle, morphology synapse, weightlessness, rat

DOI: 10.3233/VES-1993-3305

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 241-251, 1993

Authors: Suzuki, Mamoru | Harada, Yasuo | Sekitani, Tooru

Article Type: Research Article

Abstract: The vestibular organ of frogs returned from space were observed by SEM. Morphology of the sensory epithelia was normal, including ultrastructure, such as tip links and side links. The frogs’ behavior and vestibular morphology after various types of vestibular neurectomy were studied. Vestibular neurectomy resulted in tilting posture toward that side. This tilting gradually decreased to zero and the nerve regenerated. When the same nerve was cut again after postoral recovery, the tilting angle was smaller and recovery period was shorter than after the first neurectomy. When the bilateral nerves were cut and neural regeneration was inhibited on one side, …tilting slowly developed toward that side. These results show that frogs’ postural change is modified by both central compensation and peripheral vestibular function. Show more

Keywords: tilting posture, vestibular neurectomy, compensation, sensory epithelia

DOI: 10.3233/VES-1993-3306

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 253-258, 1993

Authors: Roll, J.P. | Popov, K. | Gurfinkel, V. | Lipshits, M. | André-Deshays, C. | Gilhodes, J.C. | Quoniam, C.

Article Type: Research Article

Abstract: Adaptive properties of the human proprioceptive systems were studied during the French-Soviet orbital flight (Aragatz mission, December 1988). The present space experiment investigated the hypothesis that the modifications of both biomechanical and physiological conditions occurring under microgravity involve considerable reorganization of body perception and postural control. The proprioceptive information originating in muscles is known to contribute, together with visual, vestibular, and sole cutaneous information to postural regulation. Moreover, by specifically activating the proprioceptive channel, muscle vibration is able to elicit both illusory movement sensations and postural responses. This experimental tool was used in microgravity in order to test various aspects …of muscle sensory function. Ankle flexor and extensor vibration was applied under different experimental conditions. Quantitative analysis of motor responses was carried out on leg muscle EMG, goniometric, and kinesigraphic recordings. Joystick recordings and astronauts’ comments were used to describe the kinaesthetic sensations. The main results were as follows: 1) Under microgravity, the sensitivity of muscle receptors remains unchanged. 2) During the flight, the tonic vibration reflexes (TVR) increased significantly in flexor muscles, which exhibited a sustained tonic activity. 3) The whole-body postural responses normally induced by ankle flexor muscle vibration were suppressed, whereas they remained unchanged or were only reduced when vibrations were applied to the ankle extensor muscles. In all cases, the postural response velocity decreased. 4) A disfacilitation of the vibration-induced postural illusions was observed to occur during long-term exposure to microgravity. These illusions became atypical however. For example: body lift illusion could be induced by tibialis anterior muscle vibration, whereas it was never induced in the controls. The characteristics of the illusory body movements described under normal gravity can be restored by artificially increasing the axial foot support forces during the flight. In conclusion, these data suggest that a functional reorganization of the proprioceptive information processing occurs in microgravity, affecting both perceptual and motor aspects of behavior. It is possible that these proprioceptive adaptations may be partly attributable to the new whole-body propulsive foot functions imposed by exposure to weightlessness and to the adaptation of motor behavior to the third dimension of space. Show more

Keywords: proprioception, posture, kinaesthesia, vibration, microgravity, Man, adaptation, weightlessness

DOI: 10.3233/VES-1993-3307

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 259-273, 1993

Authors: Massion, J. | Gurfinkel, V. | Lipshits, M. | Obadia, A. | Popov, K.

Article Type: Research Article

Abstract: Fast forward and backward upper trunk movements were analyzed and compared under microgravity and under preflight and postflight conditions. The kinematic analysis showed that the upper trunk movements were accompanied by hip and knee movements in the opposite direction both under microgravity and under normal gravitational conditions. This suggests that the center of mass position with respect to the feet is still regulated under microgravity when the feet are attached to the floor. The EMG analysis during backward movements shows that under preflight conditions a set of muscles (ErSp, BF, Sol) in the back of the body are activated early …on. Under microgravity, the early Sol activation was replaced by an early TA activation, which was still present at the first postflight recording and was then replaced by the early Sol activation observed under preflight conditions. This finding shows that the EMG pattern underlying the axial synergies is flexible and that adaptive changes take place both under microgravity and after return to Earth. Show more

Keywords: microgravity, equilibrium, movement, coordination, adaptation, weightlessness

DOI: 10.3233/VES-1993-3308

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 275-287, 1993

Authors: Markham, Charles H. | Diamond, Shirley G.

Article Type: Research Article

Abstract: Eye torsion was examined in 13 astronaut subjects, tested during repeated episodes of 0 G and 1.8 G in parabolic flight aboard NASA’s KC-135. Four findings are included. 1) A strong relationship between previous history of SMS and ocular torsional disconjugacy in novel gravitational states. 2) Responses were unchanged in 4 subjects retested a year later. 3) Ocular torsional disconjugacy scores increased as exposure to 0 and 1.8 G increased. This was particularly evident in subjects who had had SMS. 4) Torsional studies during 10 to 20 parabolas are required to accurately predict SMS. The hypothesis of otolith asymmetry, compensated …in 1 G but becoming unmasked in novel gravitational states, is proposed to explain the torsional disconjugacy and ensuing SMS. Show more

Keywords: space motion sickness, ocular counterrolling, otolith asymmetry, eye torsion disconjugacy

DOI: 10.3233/VES-1993-3309

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 289-295, 1993

Authors: Harm, Oeborah L. | Parker, Donald E.

Article Type: Research Article

Abstract: The research described in this paper is intended to support development and evaluation of preflight adaptation training (PAT) apparatus and procedures. Successful training depends on appropriate manipulation of visual and inertial stimuli that control perception of self-motion and self-orientation. For one part of this process, astronauts are trained to report their self-motion and self-orientation experiences. Before their space mission, they are exposed to the altered sensory environments produced by the PAT trainers. During and after the mission, they report their motion and orientation experiences. Subsequently, they are again exposed to the PAT trainers and are asked to describe relationships between …their experiences in microgravity and following entry and their experiences in the trainers. Show more

Keywords: perception, space, simulation, virtual reality, preflight adaptation training

DOI: 10.3233/VES-1993-3310

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 297-305, 1993

Authors: Mittelstaedt, H. | Glasauer, S.

Article Type: Research Article

Abstract: This contribution examines the consequences of two remarkable experiences of subjects in weightlessness, 1) the missing of sensations of trunk tilt and of the respective concomitant reflexes when the head is tilted with respect to the trunk, and 2) the persistence of a perception of “up” and “down,” that is, of the polarity of the subjective vertical (SV) in the absence of, as well as in contradiction to, visual cues. The first disproves that the necessary head-to-trunk coordinate transformation be achieved by adding representations of the respective angles gained by utricles and neck receptors, but corroborates an extant model of …cross-multiplication of utricular, saccular, and neck receptor components. The second indicates the existence of force-independent components in the determination of the SV. Although the number of subjects is still small and experimental conditions are not as homogeneous as desired, measurements and/or reports on the ground, in parabolic, and in space flight point to the decisive role of the saccular z-bias, that is, of a difference of the mean resting discharges of saccular units polarized in the rostrad and the caudad (±z-) direction. Show more

Keywords: interaction of otoliths and neck receptors, subjective vertical in weightlessness, saccular bias, force-independent components

DOI: 10.3233/VES-1993-3311

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 307-314, 1993

Authors: Oman, C.M. | Balkwill, M.D.

Article Type: Research Article

Abstract: In 1 G, the apparent time constant (Td ) of postrotatory SPV decay with the head tilted face down is 55% of that with head erect (Te ). This phenomenon is called “nystagmus dumping” and has been attributed to G effects on VOR velocity storage. Similarly, postrotatory sensation duration with head tilted (Dd ) is 32% of that when head erect (De ). In parabolic flight, Te and De are 70% of 1-G values, but a pitch back dumping movement produces no further change. Te , Td , and Dd have not previously been measured in orbital …flight. VOR and sensation duration was tested in 4 crewmembers in 4 preflight, 1 inflight (days 4 or 5) and 4 post flight sessions. Bitemporal EOG was recorded with eyes open in darkness. Instructions were to “gaze straight ahead,” and indicate when “rotation sensation disappears or becomes ambiguous”. Subjects were rotated CW and CCW head erect for 1 min at 120∘ /s, stopped, and EOG was recorded for another 1 min. This procedure was then used to study dumping, except that immediately after chair stop, subjects pitched their head forward 90∘ . SPV was calculated using order statistic filtering, and dropouts removed using an iterative model fitting method. Te and Td were determined by logarithmic linear regression of mean SPV for each subject. In orbit 90∘ pitch movement produced rapid subjective dumping, but not nystagmus dumping. Dd was noticeably shorter (“almost instantaneous”) compared in preflight Dd . Te and Td in orbit were similar to preflight Te for 3/4 subjects (rather than to preflight Td as expected). No consistent VOR gain changes were seen in orbit. Although Te is known to decrease acutely in parabolic flight, a longer time constant was measured in 3/4 subjects after 4-5 days adaptation to weightlessness, suggesting a return of angular velocity storage. Show more

Keywords: vestibular, vestibulo-ocular reflex, spatial orientation, space physiology, space shuttle

DOI: 10.3233/VES-1993-3312

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 315-330, 1993

Authors: André-Deshays, C. | Israël, I. | Charade, O. | Berthoz, A. | Popov, K. | Lipshits, M.

Article Type: Research Article

Abstract: During the long-duration spaceflight Aragatz on board the Mir station, an experiment exploring the different oculomotor subsystems involved in gaze control during orientation to a fixed target or when tracking a moving target was executed by two cosmonauts. Gaze orientation: with head fixed, the “main sequence” relationships of primary horizontal saccades were modified, peak velocity was higher and saccade duration was shorter in flight than on earth, latency was decreased and saccade accuracy was better in flight. With head free, gaze orientation toward the target was achieved by coordinated eye and head movements, their timing was maintained in the horizontal …plane; when gaze was stabilized on the target, there was a trend of a larger eye than head contribution not seen in preflight tests. Pursuit: Horizontal pursuit at 0.25 and 0.5 Hz frequency remained smooth with a 0.98 gain and minor phase lag, on earth and in flight. In the vertical plane, the eye did not track the target with a pure smooth pursuit eye movement, but the saccadic system contributed to gaze control. Upward tracking was mainly achieved with a succession of saccades, whereas downward tracking was due to combined smooth pursuit and catch-up saccades. This asymmetry was maintained during flight in head fixed and head free situations. On earth head pea velocity was maxima upward, and in flight it was maximal downward. Show more

Keywords: gaze, saccade, pursuit, eye/head, human, microgravity

DOI: 10.3233/VES-1993-3313

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 331-343, 1993

Authors: Israël, I. | André-Deshays, C. | Charade, O. | Berthoz, A. | Popov, K. | Lipshits, M.

Article Type: Research Article

Abstract: The reproduction, in complete darkness, of sequences of 5 horizontal saccades towards previously presented visual targets has been investigated in human subjects on the ground (control subjects) and one cosmonaut in microgravity. The incidence of corrective saccades during the execution of the memory-guided saccades in darkness has been examined. It was quite large for the control subjects (more than half of all saccades), and increased during the flight, while the corrective visually guided saccades incidence decreased. Direction errors occurred in about the third of all sequences on the ground, and this parameter also increased in microgravity. Memory-guided sequences were mostly …hypermetric. Whereas the absolute error continuously increased with the target rank, it was not the case with the amplitude ratio, which presented a peak at the third rank, that is, at the middle of the sequence. The accuracy of the reproduction of the sequences did depend on the sequence pattern as much as on the subject. Some learning was observed in repeated reproduction of the same pattern. Although the average error did not change in microgravity, the linear regression coefficient between the visually guided and memory-guided saccades decreased. Show more

Keywords: gaze, saccade, memory, human, microgravity

DOI: 10.3233/VES-1993-3314

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 345-360, 1993

Authors: Lackner, James R. | DiZio, Paul

Article Type: Research Article

Abstract: Exposure to weightlessness affects the control and appreciation of body position and orientation. In free fall the perception of one’s own orientation and that of the surroundings is dependent on the presence or absence of contact cues, whether part of the body is visible in relation to the architecturally defined verticals of the space craft, cognitive factors, and exposure history. Sensations of falling are not elicited in free fall when the eyes are closed or the visual field is stabilized. This indicates that visual and cognitive factors as well as vestibular ones must be implicated in the genesis of such …sensations under normal circumstances. Position sense of the limbs is also degraded in free fall. This may be due to alterations in skeletal muscle spindle gain owing to a decreased otolith-spinal activation. We provide evidence that during initial exposure to weightlessness there is a decrease in muscle stiffness which affects movement accuracy. The altered loading of the skeletal muscles due to the head and body being weightless are shown to be significant etiological factors in space motion sickness. Show more

Keywords: orientation, proprioception, muscle spindle, space motion sickness

DOI: 10.3233/VES-1993-3315

Citation: Journal of Vestibular Research, vol. 3, no. 3, pp. 361-372, 1993